Wth is wrong with halo 2?

I finished halo 3 in legendary, halo reach in legendary, im in the second level of halo CE in legendary. I am playing halo 2 in legendary but it's too hard! more than the usual, im a brigadier in halo reach and I think this is the hardest halo game ever, I am going to be a failure if I play it in heroic ?
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